When connecting pipelines such as flowlines, jumpers and risers of either rigid or flexible construction (hereinafter ‘pipelines’) to subsea connection structures, a connection tool can be used which connects to the end of the pipeline and is then brought to the connection structure where it operates to make the connection between the pipeline and connection structure. Examples of such tools are the DMaC and FTC tools of VerdErg which are described on the Internet web site www.verderg.com.
In the FTC system, a connection porch having one or more locating posts is provided at the connection structure (manifold, riser base, midwater riser, flowline termination assembly, Christmas tree, etc.). The connection tool comprises a tool chassis with a carrier mounted on the chassis and adapted to releasably carry the pipeline to be connected to the connecting structure. A pair of locating sleeves are located at the front of the chassis which slide over the posts and hold the tool adjacent the porch while the connection of the pipeline to connection structure is made.
The most controllable movements when manoeuvring the connection tool are to lower onto the locating posts and to lift off and move horizontally, either using support from the surface or with an ROV. Manoeuvres that require simultaneous horizontal and vertical movements are more difficult to control accurately.
When connecting to a riser connection on a riser tower, the porch is often downward facing requiring the end of the pipeline to face upwards when the connection is made. The FTC connection tool addresses this by allowing the chassis to pivot on the locating sleeves so as to swing into the required position. In this way, the tool can be engaged on the locating posts by a vertical movement. However, when lifting the tool off the locating posts at the end of the connection process, problems can occur if the load of the connection tool is not appropriately distributed on the lifting mechanism. If the load is incorrectly distributed, the connection tool can swing in an uncontrolled way as soon as the sleeves disconnect from the locating posts, potentially causing damage to the connection structure or other installations.
It is an object of the invention to provide a system that helps ensure even distribution of the load on disconnection by ensuring that the connection tool is properly oriented before it is allowed to disconnect from the locating posts.